

Yes yes yes yes yes
Raid1 that thing and sleep easier. Good on you for having a cold spare, and knowing to buy your drives at different locations/times to get different batches. Your head is in the right place! No reason to leave that data unprotected if you have the underlying tech and hardware.
Initiator Target mode and Host Bus Adapter mode are interchangable terms for the same thing. The card has 2 modes, one is RAID (don’t use this) and the other is Initiator-Target or HBA mode.
ZFS needs direct disk access so flash the IT .bin for HBA mode using the P20 (latest) drivers and you’re g2g.